Fire Recovery Realities

Tips On Properly Insulating A Crawl Space

by Matthew Fields

An inadequately insulated crawl space can cause discomfort and lead to cold areas in a home regardless of how high the heat gets turned up. That's because crawl spaces tend to be damp, open spaces that often harbor cold, drafty air. 

While crawl spaces can cause a lot of practical problems in maintaining a comfortable home, they are a popular foundation solution for builders because crawl space foundations are quick and easy to build. If you have a crawl space in your home, you can improve its insulation with the following procedures.

Is your crawl space ventilated?

The best way to insulate your crawl space will depend on whether or not it's ventilated. Usually, crawl spaces are ventilated to prevent the buildup of moisture. However, crawl spaces are occasionally left unventilated to improve heating during the cold months or to prevent moisture problems caused by humid summer weather. 

Insulating a ventilated crawl space

  • Cut off sources of moisture- Whether a crawl space is vented or not, it needs to be protected from moisture sources. Common sources of moisture in crawl spaces are exterior fixtures like downspouts and gutters that are pointing towards the crawl space.
  • Seal holes- In a ventilated crawl space, air should only be entering through vents. Other holes that are allowing air flow into the crawl space need to be sealed.
  • Insulate with rolled fiberglass between floor joists- Rolled fiberglass insulation can be installed against the subfloor, and seams should be sealed off to prevent wind and drafts from reaching the insulation.
  • Put a vapor barrier over insulation- Insulation needs to be protected from moisture. Rolled fiberglass insulation can be covered with a house-wrap or faced with a vapor barrier.

Insulating an unventilated crawl space

  • Cut off sources of moisture- As with ventilated crawl spaces, sources of moisture need to be stopped and prevented from causing moisture buildup.
  • Comply with building codes- In some areas, crawl spaces are required to be ventilated by building codes. If you have an unventilated crawl space, you should make sure that both your crawl space and your proposed insulation improvements comply with applicable codes.
  • Seal foundation vents and air leaks- Foundation vents and air leaks needs to be sealed off to protect an unventilated crawl space from unwanted air flow.
  • Use batt or rigid foam board insulation- Insulating with batt or rigid foam board is a good solution for unventilated crawl spaces. A vapor barrier should be attached to insulation batts to protect from moisture.
  • Install a termite shield- Unventilated crawl spaces can be protected against infestation by a termite shield between the masonry foundation wall and band joist.